Feasibility study of a current mode gamma radiation dosimeter based on a commercial pin photodiode and a custom made auto-ranging electrometer

An experimental study has been conducted to evaluate the feasibility of a current mode gamma radiation dosimeter, consisting of a commercial PIN photodiode as a radiation sensor, and a custom made auto-ranging electrometer for real-time measurement of the PIN photodiode’s response under radiation exposure. The radiation induced direct current response for single PIN photodiodes with different active areas, as well as for multiple PIN photodiodes connected in parallel, has been investigated. Three types of commercial silicon PIN photodiodes have been chosen for evaluation - S1223, BPW34, and PS100-6-CER2 PIN. During the experiment, five samples have been tested - three samples made of single PIN photodiodes (one sample of each photodiode type) and two samples formed by connecting multiple photodiodes in parallel (two BPW34 photodiodes in parallel and four BPW34 photodiodes in parallel). The samples have been irradiated with a 60Co gamma ray source and the relations between the induced photocurrent and the dose rate, and between the accumulated charge and the absorbed dose, have been determined. For measuring the photodiodes response, a custom made auto-ranging electrometer controlled by a personal computer, and capable of measuring direct currents from 50 pA to 10 mA with relative error less than 2.5%, has been used. Obtained results have shown very good linearity between the dose rate and the induced photocurrent for dose rates ranging from 0.93 Gy/h to 67 Gy/h. Also, very good linearity has been observed between the accumulated charge and the absorbed dose for all tested samples, within the investigated range of absorbed doses from 472 mGy to 3.3 Gy. On the basis of the obtained results, a simple model has been derived, enabling the estimation of the photodiode’s current response as a function of the dose rate and the photodiode’s geometry (active area and depletion layer width). [Projekat Ministarstva nauke Republike Srbije, br. 43011

Radiation sensitive MOSFETs irradiated with various positive gate biases

The RADiation sensitive metal-oxide-semiconductor field-effect-transistors (RADFETs) were irradiated with gamma rays up to absorbed dose of 110 Gy(H2O). The results of threshold voltage, VT, during irradiation with various positive gate biases showed the increase in VT with gate bias. The threshold voltage shift, ΔVT, during irradiation was fitted very well. The contributions of both the fixed traps (FTs) and switching traps (STs) during radiation on ΔVT were analyzed. The results show the significantly higher contribution of FTs than STs. A function that describes the dependence of threshold voltage shift and its components on gate bias was proposed, which fitted the experimental values very well. The annealing at the room temperature without gate bias of irradiated RADFETs was investigated. The recovery of threshold voltage, known as fading, slightly increase with the gate bias applied during radiation. The ΔVT shows the same changes as the threshold voltage component due to fixed states, ΔVft, while there is no change in the threshold voltage component due to switching traps, ΔVst

Anthropometric parameters and aesthetics in the making of fixed prosthodontic restaurations: Part 2

Introduction: The role of aesthetic dentistry in the field of fixed dental prosthetics is to redesign the smile, which means not only the treatment on the teeth, but also the treatment of the surrounding soft tissues. Successful therapy can be achieved by establishing the harmony between the static (teeth, gingiva) and dynamic factors (lips, cheeks, mimic muscles) at rest and when performing various functions of the orofacial system. The aim: of the study was to analyze the parameters of the oral soft tissues (gingival health, gingival height, gingival zeniths, lip line and symmetry and balance of the dentition) that affect the aesthetics of fixed prosthodontic restorations. Literature data and clinical experience were used. Conclusion: Adherence to the described parameters is of great importance in the development of aesthetic and functional fixed prosthetic restoration

Antioxidant and Antimicrobial Activity of Polyphenol Extracts from Wild Berry Fruits Grown in Southeast Serbia

Purpose: To assess the antioxidant and antimicrobial activities of polyphenolic extracts of three wild red wild berry fruit species from Southeast Serbia, viz, European cornel ( Cornus mas ), blackthorn ( Prunus spinosa L.) and wild blackberry ( Rubus fruticosus ). Methods: Polyphenol content was determined using spectrophotometric and High performance liquid chromatography (HPLC) methods. Antioxidant activity was estimated by 2,2`- diphenyl - 1 - picrylhydrazyl (DPPH) test while reliminary antimicrobial tests were carried out by disc diffusion method in which antibacterial activity was evaluated by measuring the zone of inhibition against test bacterial strains. Broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results: The highest amount of total phenols was found in European cornel (8625.89 mg kg-1FW). Galic acid, caffeic acid, p-coumaric acid, ferulic acid, (+)-catechin, procyanidin B2, (-)-epicatechin, quercetin, rutin and quercetin-3-glucoside were the main polyphenols in the fruit extracts. All extracts showed high scavenging effect on DPPH radical with IC50 values ranging from 22.19 to 31.18 ml g-1, as well as high antimicrobial activity on almost all the tested bacterial strains. Conclusion: Extracts of wild berry fruits may be suitable for the preparation of medicinal and nutritional products

Phenol composition, DPPH radical scavenging and antimicrobial activity of cornelian cherry (Cornus mas) fruit and leaf extracts

Fruit is rich in different phenolic compounds which are recognized as potential natural medicaments and have been used in folk medicine for centuries. In order to evaluate phenol composition, cornelian cherry (Cornus mas) fruit and leaf extracts were subjected to the spectrophotometric and HPLC analysis. The radical scavenging activity was estimated using DPPH test and antimicrobial activity by disc diffusion and microwell dilution tests. All extracts showed high phenol content from 89.89 ± 0.45 to 117.34 ± 1.40 mg f gallic acid equivalents GAE/g extract dry matter DM but different composition of phenol compounds. Flavonols, anthocyanins, flavan-3-ols and phenolic acids were the main phenol classes found in the investigated fruit and leaf extracts. All extracts showed significant radical scavenging activity and a correlation with total phenol content (R2 = 0.9832). Significant antimicrobial activity was found against Gram-positive, followed by Gram-negative strains, and yeast in all tested extracts. Cornelian cherry fruit and leaf extracts, rich in phenolic content, with significant antiradical and antimicrobial activity, can be used as additives in food and medicaments. [Projekat Ministarstva nauke Republike Srbije, br. 34012, br. 31020 and br 176006 and EU, FP7 - Regpot - 2007- 3-01, the project «Chromlab-Antioxidant», No. 204756

Precipitation effect of ferrofluids under the influence of the external magnetic field

Light transmitting measuerements of white light and laser beam propagating through FeFe2O4, CoFe2O4, and MgFe2O4 nanoparticles coated with citric and oleic acid, under the influence of an external magnetic field in the range of 30-400 mT, were presented. Under the influence of external magnetic field, the change of transmittance occured and a precipitation of all studied samples was obtained. To the best of our knowledge, the field-induced precipitation effect of ferrites was not analysed so far and its significance and the influence on the further laser treatment of the patients previously exposed to the ferrite-based MRI agents is not well recognized. This should be of great importance, since neglecting of the precipitation would lead ti inapropriate response when patients are treated by diagnostic and therapy methods

Synergistic effect of Gentiana lutea L. on methyl methanesulfonate genotoxicity in the Drosophila wing spot test

Ethnopharmacological relevance: Gentiana lutea L., the yellow gentian, is herb known for its pharmacological properties, with a long tradition of use for the treatment of a variety of diseases including the use as a remedy for digestion, also in food products and in bitter beverages. The aim of the present study is to evaluate, for the first time, genotoxicity of gentian alone, and its antigenotoxicity against methyl methanesulfonate (MMS). Materials and methods: The water infusion of the underground part of gentian were evaluated in vivo using the Drosophila wing spot test, at the dose commonly used in traditional medicine. For antigenotoxic study two types of treatment with gentian and MMS were performed: chronic co-treatment, as well as post-treatment with gentian after acute exposure with MMS. Results: Water infusion of gentian alone did not exhibit genotoxicity. The results of co- and post-treatment experiments with gentian show that gentian enhanced the frequency of mutant clones over the values obtained with MMS alone, instead of reducing the genotoxicity of MMS, for 22.64% and 27.13% respectively. Conclusions: This result suggests a synergism of gentian with MMS, and indicates that water infusion of gentian used in traditional medicine may have particular effects with regard to genotoxicity indicating careful use. (C) 2013 Elsevier Ireland Ltd. All rights reserved.Ministry of Education, Science and Technological Development, Republic of Serbia [173012

Power Silicon Carbide Schottky Diodes as Current Mode γ - Radiation Detectors

In this paper, the feasibility of using commercial power Silicon Carbide (SiC) Schottky diodes as a current mode γ-radiation detector have been examined. Diodes with almost identical electric characteristics are purchased from two different manufacturers, On Semiconductor and RoHM. They have been tested under gamma radiation exposure from a Co-60 source. The current response during irradiation has been measured for various dose rates with reversed diode bias. Investigated range of dose rates was from 0.258 Gy/h to 26.312 Gy/h, and reverse diode bias values were 10 V, 20 V, 50 V, 100 V and 200 V. Tested Schottky diodes produce stable current response for the investigated dose rates. Although the manufacturers are different, the results show that the dosimetric characteristics of these diodes have an excellent match. Sensitivity was proportional to the applied reverse bias voltage. A simple power-law can very well describe the dependence of measured radiation-induced current on dose rate

Sensitivity of Unbiased Commercial P-channel Power VDMOSFETs to X-ray Radiation

The effect of X-rays on the p-channel power vertical double diffused metal-oxide-semiconductor field-effect transistors (VDMOSFETs) was investigated. The VDMOSFETs were irradiated without gate polarization using three different Xray beams. Due to the polyenergetic nature of X-rays, their effect is much more complex than the effect of gamma radiation on transistors. The influence of X-rays on threshold voltage shift $(\Delta V_T)$ and on the creation of fixed traps (FTs) in gate oxide and on switching traps (STs) near and at oxide/semiconductor interface was analyzed. The effect of STs on T is more significant than in the case of y-radiation. The obtained results showed that the sensitivity to radiation depends on the radiation energy, and they are in accordance with the theoretical predictions

Sensitivity analysis for daily building operation from the energy and thermal comfort standpoint

Improving energy performance of buildings is one of the most important tasks for reaching sustainability. Assessing building energy consumption is performed more often with specialized simulation tools. Sensitivity analysis proved to be a valuable tool for creating more reliable and realistic building energy models and better buildings. This paper briefly describes the methodology for running global sensitivity analysis and tools that can be used, and presents the results of such an analysis conducted for winter period, daily, on input variables covering a real building's operation, control and occupant related parameters that affect both thermal comfort and heating energy consumption. Two sets of inputs were created. The only difference between these sets is an addition of clothing insulation and occupant heat gain as input variables. The reference building was simulated for three distinctive winter weeks. Two additional input variables have an effect especially on thermal comfort, but they do not disturb the relative order of other influential input variables. The common influential variables for both energy consumption and thermal comfort were identified and are: air handling unit sup-ply temperature and airflow rate and control system related parameters. This can help in future research into implementing the simulation-assisted optimized operation in real buildings. [Projekat Ministarstva nauke Republike Srbije, br. TR-33051: The concept of sustainable energy supply of settlements with energy efficient buildings